Here's an extract from the English version of Wikipedia regading LP lengths.
When initially introduced, 12-inch LPs played for a maximum of 45 minutes, divided over two sides. However, in 1952, Columbia Records began to bring out extended-play LPs that played for as long as 52 minutes, or 26 minutes per side. These were used mainly for the original cast albums of some Broadway musicals, such as Kiss Me, Kate and My Fair Lady, or in order to fit an entire play, such as the 1950 production of Don Juan in Hell, onto just two LPs.
The 52+ minute playing time remained rare, however, because of mastering limitations, and most LPs continued to be issued with a 30- to 45-minute playing time throughout the lifetime of their production. However, some albums would eventually exceed even the 52-minute limitation, with single albums going to as long as ninety minutes in the case of Arthur Fiedler's 1976 LP 90 Minutes with Arthur Fiedler and the Boston Pops, made by Radio Shack. However, such records had to be cut with much narrower spacing between the grooves, which allowed for a much smaller amount of dynamic range on the records, and meant that playing the record with a worn needle could damage the record.
It also resulted in a much quieter sound. (Other notably long albums included the UK version of The Rolling Stones' Aftermath; La Monte Young's Dream House 78' 17", whose two sides were each just under 40 minutes; Bob Dylan's 1976 album Desire, with side two being just shy of thirty minutes; Brian Eno's 1975 album Discreet Music, whose A-side exceeded thirty minutes; and Todd Rundgren's Initiation, totalling 67:32 over two sides).
Spoken word and comedy albums, not having a wide range of musical instrumentation to reproduce, can be cut with much narrower spacing between the grooves; for example, The Comic Strip, released by Springtime Records in 1981, has a Side A lasting 38:04 and a Side B lasting 31:08, for a total of 69:12.